Method and apparatus for performing discontinuous reception operation by connected mode user equipment in a mobile communication system

ABSTRACT

Methods and apparatuses are provided for establishing time alignment by a User Equipment (UE) in a wireless communication system. Information for identifying a dedicated preamble on a downlink control channel is received from a base station. The dedicated preamble is transmitted to the base station based on the information. A response message to the transmitted dedicated preamble is received from the base station on a downlink shared channel. The response message includes a timing adjustment information and information for a Channel Quality Indicator (CQI) report. Time alignment is established based on the timing adjustment information included in the response message. The CQI report based on the information for CQI report is transmitted to the base station.

PRIORITY

This application is a Continuation Application of U.S. application Ser.No. 14/968,315, filed in the U.S. Patent and Trademark Office (USPTO) onDec. 14, 2015, which is a Continuation Application of U.S. applicationSer. No. 14/664,263, filed in the USPTO on Mar. 20, 2015, now U.S. Pat.No. 9,215,681, issued on Dec. 15, 2015, which is a ContinuationApplication of U.S. application Ser. No. 14/478,702, filed in the USPTOon Sep. 5, 2014, now U.S. Pat. No. 9,007,977, issued on Apr. 14, 2015,which is a Continuation Application of U.S. application Ser. No.13/739,762, filed in the USPTO on Jan. 11, 2013, now U.S. Pat. No.8,831,045, issued on Sep. 9, 2014, which is a Continuation Applicationof U.S. application Ser. No. 11/857,976, filed in the USPTO on Sep. 19,2007, now U.S. Pat. No. 8,379,570, issued on Feb. 19, 2013, which claimspriority under 35 U.S.C. § 119(a) to Korean Patent Application Nos.10-2006-0090668 and 10-2007-0016815, filed in the Korean IntellectualProperty Office on Sep. 19, 2006 and Feb. 16, 2007, respectively, thedisclosures of each of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to a mobile communicationsystem, and in particular, to a Discontinuous Reception (DRX) method andapparatus for minimizing power consumption by a User Equipment (UE) in aconnected mode or connected state, referred to herein as a connectedmode UE.

2. Description of the Related Art

A Universal Mobile Telecommunication Service (UMTS) system is a 3^(rd)generation asynchronous mobile communication system that uses WidebandCode Division Multiple Access (CDMA) based on Global System for MobileCommunications (GSM) and General Packet Radio Services (GPRS), both ofwhich are European mobile communication systems.

The 3^(rd) Generation Partnership Project (3GPP) is in charge of UMTSstandardization, and Long Term Evolution (LTE) is now under discussionas a next generation mobile communication system of the UMTS system.

LTE is a technology for realizing high-speed packet-based communicationhaving a data rate of a maximum of about 100 Megabits per second (Mbps).To this end, several schemes are under discussion including, forexample, a scheme for reducing the number of nodes located in thecommunication path by simplifying a configuration of the network, and ascheme for maximally approximating wireless protocols to wirelesschannels.

FIG. 1 shows a DRX operation of a connected mode UE according to theprior art.

Shown in FIG. 1 is an example of a communication system to which Node Bscheduling is applied. Therefore, the UE supports uplink packet servicesover transmission resources allocated depending on the schedulinginformation from the Node B. Further, the Node B determines a Modulationand Coding Scheme (MCS) according to the quality of the allocatedchannel, and supports reception gain of the UE by applying HybridAutomatic Repeat reQuest (HARQ).

Referring to FIG. 1, the UE is a UE in the mode (or state) where the UEis Radio Resource Control (RRC)-connected to an upper layer. To savepower, the connected mode UE, while keeping a sleep mode for a cyclehaving a particular length determined in an upper layer, wakes up attimings 105, 115, 120 and 125, and checks a downlink control channelallocated from the Node B to determine whether there is any data toreceive. At timings 105, 120 and 125, there is no data to receive. Attiming 115, there is data to receive. When there is no data to receive,e.g. at timings 105, 120 and 125, the UE switches (transitions) to thesleep mode and keeps the sleep mode until the next wake-up timing.

However, when there is any data to receive, as at timing 115, the UEreceives the data from the Node B in step 140, and performs a process instep 145 of sending a response signal (ACK/NACK) indicating receptionsuccess/failure of the data transmitted based on HARQ. Thereafter, whenthe Node B sends a signal indicating that there is no more data totransmit, the UE stops the data reception and switches back to the sleepmode.

For convenience, the timing at which the UE wakes up is referred toherein as wake-up timing, and the time interval between the wake-uptimings is referred to herein as DRX cycle length 110. The connectedmode UE reduces power consumption through the DRX operation.

The UE receives signaling information, based on which the UE cancalculate the wake-up timing, from the Node B in the call setup process.The wake-up timing is generally calculated as shown in Equation (1).Wake-Up Timing=First Wake-Up Timing+n×DRX Cycle Length  (1)

The first wake-up timing is generally calculated using constantinformation, such as, for example, an identifier of the UE, and the DRXcycle length is set by the Node B according to types of services and isthen notified to the UE.

In the DRX operation, when the length of the DRX cycle is set long, theconnected mode UE that performs no data transmission/reception for theDRX cycle, may probably suffer from uplink synchronization loss.

For example, a UE employing Adaptive Modulation and Coding (AMC) shouldperiodically report the channel quality (or channel status) of the UE tothe Node B at a particular timing. A connected mode UE, operating in adiscontinuous transmission/reception mode, periodically reports thechannel quality using a particular channel at a particular timing beforethe wake-up timing. This conventional channel quality report is veryinefficient in that the UE reports the channel quality even when thereis no need for actual data reception.

Therefore, a need exists for a discontinuous transmission/receptionoperation to minimize power consumption of a connected mode UEsupporting a next generation mobile communication system, therebysolving problems of the prior art.

In addition, a need exists for an efficient channel quality reportprocedure and uplink synchronization procedure of the connected mode UE,distinguishable from conventional ones, for a next generation mobilecommunication system.

SUMMARY OF THE INVENTION

The present invention addresses at least the above-described problemsand/or disadvantages and provides at least the advantages describedbelow. Accordingly, an aspect of the present invention is to provide amethod and apparatus for minimizing power consumption in receiving databy a connected mode UE in a mobile communication system.

Another aspect of the present invention is to provide a method andapparatus for minimizing power consumption in receiving downlink data bya connected mode UE operating in a discontinuous transmission/receptionmode in a mobile communication system.

Another aspect of the present invention is to provide a method andapparatus for establishing uplink synchronization and receiving downlinkdata by a connected mode UE operating in a DRX mode in a mobilecommunication system.

According to an aspect of the present invention, a method is providedfor establishing time alignment by a UE in a wireless communicationsystem. Information for identifying a dedicated preamble on a downlinkcontrol channel is received from a base station. The dedicated preambleis transmitted to the base station based on the information. A responsemessage to the transmitted dedicated preamble is received from the basestation on a downlink shared channel. The response message includes atiming adjustment information and information for Channel QualityIndicator (CQI) report. Time alignment is established based on thetiming adjustment information included in the response message. The CQIreport based on the information for CQI report is transmitted to thebase station.

According to another aspect of the present invention, a UE is providedfor establishing time alignment in a wireless communication system. TheUE includes a transceiver for receiving, from a base station,information for identifying a dedicated preamble on a downlink controlchannel, transmitting the dedicated preamble based on the information tothe base station, receiving from the base station a response messagecorresponding to the transmitted dedicated preamble on a downlink sharedchannel, and transmitting a CQI report to the base station. The responsemessage includes a timing adjustment information and information for theCQI report. The UE also includes a controller operable to establish timealignment based on the timing adjustment information included in theresponse message, and to transmit, to the base station, the CQI reportbased on the information for the CQI report.

According to still another aspect of the present invention, a method isprovided for establishing time alignment by a base station in a wirelesscommunication system. Information for identifying a dedicated preambleon a downlink control channel is transmitted to a UE. The dedicatedpreamble is received from the UE based on the information. A responsemessage corresponding to the transmitted dedicated preamble istransmitted to the UE on a downlink shared channel. The response messageincludes timing adjustment information for establishing time alignmentand information for a CQI report. The CQI report is received from the UEbased on the information for CQI report.

According to yet another aspect of the present invention, a base stationis provided for establishing time alignment in a wireless communicationsystem. The base station includes a transceiver for transmitting, to aUE, information for identifying a dedicated preamble on a downlinkcontrol channel, receiving, from the UE, the dedicated preamble based onthe information, transmitting, to the UE, a response messagecorresponding to the transmitted dedicated preamble on a downlink sharedchannel, and receiving, from the UE, a CQI report. The base station alsoincludes a controller operable to generate the response messageincluding timing adjustment information for establishing time alignmentand information for the CQI report, and to receive, from the UE, the CQIreport based on the information for the CQI report.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 illustrates a DRX operation of a connected mode UE according tothe prior art;

FIG. 2 illustrates a next generation mobile communication system towhich the present invention is applicable;

FIG. 3 illustrates a DRX operation of a connected mode UE according to afirst embodiment of the present invention;

FIG. 4 is a flowchart illustrating a DRX operation of a connected modeUE according to the first embodiment of the present invention;

FIG. 5 illustrates a DRX operation of a connected mode UE according to asecond embodiment of the present invention;

FIG. 6 is a flowchart illustrating a DRX operation of a connected modeUE according to the second embodiment of the present invention;

FIG. 7 illustrates a conventional uplink synchronization establishmentprocess of an idle mode UE;

FIG. 8 illustrates a DRX operation of a connected mode UE according to athird embodiment of the present invention;

FIG. 9 is a flowchart illustrating an operation of a UE according to thethird embodiment of the present invention; and

FIG. 10 is a block diagram of a reception apparatus of a UE according tothe present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

Preferred embodiments of the present invention will now be described indetail with reference to the annexed drawings. In the followingdescription, a detailed description of known functions andconfigurations incorporated herein has been omitted for clarity andconciseness.

Although the present invention will be described herein with referenceto a Long Term Evolution (LTE) system, by way of example, the same canbe applied to all communication systems employing a DiscontinuousReception (DRX) mode without separate modification. In addition, thepresent invention can be applied to mobile communication systemsemploying Node B scheduling without separate modification. Further, thepresent invention can be applied to communication systems employingHybrid Automatic Repeat reQuest (HARQ) and communication systemssupporting uplink services.

In particular, a User Equipment (UE) can perform uplink transmissionafter uplink synchronization is established in a communication systemusing Orthogonal Frequency Division Multiplexing (OFDM) as a wirelessaccess technology.

The phrase ‘establishing uplink synchronization’ as used herein refersto adjusting transmission timing of the UE so a transmission signal ofthe UE is located within a specific time interval called Cyclic Prefix(CP) at the Node B arrival timing. The uplink synchronization isestablished in a way that the UE transmits a particular preamble over anuplink shared channel, receives timing adjustment information from theNode B, and then adjusts uplink transmission timing according to thetiming adjustment information.

The uplink synchronization, once established, is kept while thedownlink/uplink data transmission/reception continues. However, theuplink synchronization may be lost in the state where there is no datatransmission/reception for a long time. Therefore, if the connected modeUE has not performed data transmission/reception for a longer thanpredetermined time due to the DRX, there is high possibility that theNode B cannot transmit data to the connected mode UE because the uplinksynchronization is not established.

Therefore, in the present invention, before transmitting data to aconnected mode UE that has not performed data transmission/reception fora long time due to the DRX, the Node B sends an ‘incoming dataindication’ indicating presence of transmission data to the UE, so theUE matches uplink synchronization before receiving the data. Inaddition, upon receipt of the incoming data indication, the connectedmode UE reports a measured downlink channel quality value, therebyfacilitating efficient downlink data transmission/reception.

The present invention provides a scheme for applying discontinuoustransmission/reception to the connected mode UE to allow the UE tominimize power consumption of the UE. Particularly, in the DRX mode, theconnected mode UE, only when the UE receives an incoming dataindication, matches uplink synchronization, reports channel quality ofthe UE, and then performs data reception.

In other words, in the present invention, when the Node B has data totransmit to a particular connected mode UE, the Node B first sends anincoming data indication to the UE that has waken up at the wake-uptiming, before data transmission, and the UE, before data reception,first establishes uplink synchronization and reports channel quality ofthe UE. Therefore, in the present invention, the uplink synchronizationremains established before the UE receives at least one data burst, andthe UE reports the channel quality only when there is data to receive.This is because periodically reporting the channel quality by the UE isinefficient when the UE operates in the DRX mode in the connected mode.

As described above, in the present invention, when the connected mode UEoperates in the DRX mode, the UE reports the channel quality only at thescheduled data reception timing, i.e. only when the UE receives anincoming data indication, thereby preventing unnecessary channel qualityreport and increasing efficiency of the DRX mode.

In addition, the phrases ‘transmission data indication information’ and‘indication information indicating transmission of downlink data’, asused herein, have the same meaning as the incoming data indication, andare interchangeably used.

Further, the connected mode UE according to the present invention is aUE in the mode where the UE is Radio Resource Control (RRC)-connected tothe upper layer. This means a new-mode UE distinguishable from the3^(rd) Generation Partnership Project (3GPP) idle mode UE thatdetermines whether there is any signaling from the upper layer using theDRX parameters determined in the state where there is no existing RRCconnection.

FIG. 2 shows an example of a next generation mobile communication systemto which the present invention is applicable.

In FIG. 2, Evolved UMTS Radio Access Networks (E-RANs) 210 and 212 eachare simplified to a 2-node configuration of Evolved Node Bs (ENBs, orNode Bs) 220, 222, 224, 226 and 228, and anchor nodes (Evolved GatewayGeneral Packet Radio Services (GPRS) Service Node (EGGSN)) 230 and 232.A UE 201 accesses an Internet Protocol (IP) network 214 via the E-RAN210.

The ENBs 220 to 228 each correspond to the existing Node B of the UMTSsystem, and are connected to the UE 201 over wireless channels. Unlikethe existing Node B, the ENBs 220 to 228 perform complex functions. InLTE, because all user traffics including real-time services, such asVoice over IP (VoIP), are serviced over a shared channel, there is aneed for an apparatus for collecting channel quality information of UEsand performing scheduling depending thereon, and this is managed by theENBs 220 to 228.

To realize a data rate of a maximum of 100 Mbps, LTE may use OFDM as awireless access technology in a 20-MHz (Megahertz) bandwidth. Further,LTE may employ Adaptive Modulation & Coding (AMC) that adaptivelydetermines a modulation scheme and a channel coding rate according tothe channel quality of the UE.

To employ AMC, the UE reports channel quality of the UE to the Node B.In this case, the UE, while transitioning to the connected mode, isallocated a channel to be used for the channel quality report, andperiodically reports the channel quality over the allocated channel.

Therefore, in the present invention, when the connected mode UE operatesin the DRX mode, the UE reports the channel quality only at thescheduled data reception timing, i.e. only when the UE receives anincoming data indication, thereby preventing unnecessary channel qualityreport and increasing efficiency of the DRX mode.

Although HARQ is performed between the ENBs 220 to 228 and the UE 201even in the LTE system like in the communication system supporting theHigh Speed Downlink Packet Access (HSDPA) or Enhanced uplink DedicatedChannel (E-DCH) service, Outer ARQ can be performed in the upper layerbecause meeting various Quality of Service (QoS) conditions is notpossible with only the HARQ. The Outer ARQ other than ARQ is performedbetween the UE 201 and the ENBs 220 to 228. In addition, the sharedchannel to which the present invention is applied, as used herein,refers to a channel serving as HS-PDSCH (in HSDPA) or E-DPDCH (in E-DCH)over which user traffics are transmitted.

Many next generation mobile communication systems including the LTEsystem use HARQ as an error correction technique. HARQ refers to atechnique for soft-combining previously received data with retransmitteddata without discarding the previously received data, thereby increasinga reception success rate. More specifically, a receiving HARQ entitydetermines presence/absence of error in a received packet, and thensends a HARQ positive Acknowledgement (HARQ ACK) signal or an HARQnegative Acknowledgement (HARQ NACK) signal to a transmitting HARQentity according to the determination result.

Therefore, the transmitting HARQ entity performs retransmission of theHARQ packet or transmission of a new HARQ packet according to the HARQACK/NACK signal. Further, the receiving HARQ entity soft-combinesretransmitted packet with the previously received packet, therebyreducing the error occurrence rate.

In a communication system employing Node B scheduling, a scheduler ofthe Node B may allocate transmission resources to a corresponding UE totransmit a user packet to the UE or to allow the UE to transmit a userpacket, and a corresponding transmission resource allocation message issignaled to the UE over a channel. For convenience, the channel overwhich the transmission resource allocation message is transmitted isreferred to herein as a grant channel.

In OFDM, a transmission resource refers to a particular frequency bandfor a particular interval. An LTE system may divide a full systemfrequency band into 24 bandwidths and use them as transmissionresources, and the Node B may allocate some of the 24 bandwidths to theUE for 0.5 milliseconds (msec). The transmission resource allocationmessage includes (i) an identifier of the UE that is an identifier ofthe UE scheduled to be allocated transmission resources, (ii)transmission resource information regarding transmission resourcesallocated to the UE, and (iii) other information, such as a length of avalid period of the transmission resources or the like.

The UE, upon receiving a transmission resource allocation messagecontaining the identifier of the UE over the grant channel, receives ortransmits data over the allocated transmission resources.

In brief, in the present invention, when the connected mode UE operatesin the DRX mode, the Node B first sends an incoming data indication tothe UE before the actual data transmission. After receiving the incomingdata indication, the UE matches uplink synchronization and reportschannel quality of the UE, thereby facilitating efficient datareception. In this way, the present invention allows the UE operating inthe DRX mode to establish uplink synchronization and report the channelquality of the UE only when the UE actually has data to transmit,thereby setting the DRX cycle long and minimizing power consumption ofthe UE.

FIG. 3 shows a DRX operation of a connected mode UE according to a firstexample of the present invention.

In FIG. 3, in a call setup process, upon receipt of DRX-relatedparameters signaled from a Node B, a UE calculates a wake-up timingusing the DRX-related parameters. The DRX-related parameters caninclude, for example, a DRX cycle length 310, first wake-up timingcalculation information, t1, t2, etc.

The DRX cycle length 310 indicates a length of a period between wake-uptimings, and the Node B selects an appropriate value according to typesof services. The Node B uses a long DRX cycle length for the servicesless susceptible to the delay, and a short DRX cycle length for theservices highly susceptible to the delay.

First wake-up timing calculation information can be first wake-up timingdirectly signaled to the UE, or can be first wake-up timing informationthe UE can calculate by combining the identifier of the UE, the DRXcycle length, etc.

t1 indicates a period between the timing when the UE receives anincoming data indication and the timing when the UE receivestransmission resource information over the grant channel.

t2 indicates a period between the timing when the UE receives anincoming data indication and the timing when the UE sends channelquality report information. The UE, after establishing uplinksynchronization, keeps the sleep mode until the timing when the UEperforms the channel quality report.

After the call setup is completed, the UE calculates the first wake-uptiming, and then calculates the next wake-up timing by adding a multipleof a length of the DRX cycle to the first wake-up timing.

The connected mode UE transitions to the sleep mode until the calculatedwake-up timing, and monitors a particular downlink control channel atthe corresponding particular wake-up timing 315.

The downlink control channel includes an incoming data indication forthe UE, and if the UE fails to receive the incoming data indication instep 330, the UE transitions back to the sleep mode and keeps the sleepmode until the next wake-up timing 320. The UE re-monitors the downlinkcontrol channel at the next wake-up timing 320.

The Node B sends an incoming data indication to the UE over the downlinkcontrol channel at the wake-up timing 320 in step 340 when the Node Bdetermines at an arbitrary time that the Node B has data stored in abuffer to transmit to the UE.

Therefore, upon receipt of the incoming data indication, the UE that haswaken up at the wake-up timing 320, starts timers to which the t1 and t2are input, and performs an uplink synchronization establishmentoperation in step 345. In this case, the UE can skip the uplinksynchronization establishment process when the UE determines that theuplink synchronization has already been established.

For example, if a particular period has not elapsed yet after the UEperformed data transmission/reception, the UE can determine that theuplink synchronization is being kept. Alternatively, if the sub-frameboundary of the current timing is similar to the sub-frame boundary thatthe UE has previously recognized while establishing the uplinksynchronization, the UE can determine that the uplink synchronization isbeing kept.

After completing the uplink synchronization establishment process, theconnected mode UE keeps the sleep mode again until the t2 timer used forsending the channel quality report expires.

After the t2 timer expires in step 367, the UE reports the CQI of the UEusing a particular channel in step 350. The channel quality isinformation based on which the Node B can determine an appropriate MCSlevel and transmission power, and the UE reports the channel qualitybased on received equality measurement results on particular downlinkpilot channels.

A channel previously allocated to the UE can be used as the channel overwhich the channel quality information is transmitted. Alternatively, theNode B can signal information on the channel used for making the channelquality report on the incoming data indication, after dynamicallyallocating the channel over which the UE will transmit the channelquality information.

After the above processes are completed, the UE switches to the sleepmode and keeps the sleep mode again until t1 expires.

If the set t1 expires in step 370, the connected mode UE wakes up andreceives a transmission resource allocation message in step 355. Thetransmission resource allocation message, provided for sending downlinktransmission resources to the UE over the grant channel, includesidentifier information of the UE, transmission resource information, andvalid period information of the transmission resources.

Thereafter, the connected mode UE receives data over the allocateddownlink transmission resources in step 360, and performs a particularHARQ process on the received data in step 365. Upon receiving from theNode B a signal indicating that there is no more transmission data, theUE switches to the sleep mode and keeps the sleep mode until the nextwake-up timing 325.

FIG. 4 shows a DRX operation of a connected mode UE according to thefirst example of the present invention.

In step 405 of FIG. 4, the UE receives DRX cycle length, first wake-uptiming calculation information, t1, and t2 signaled from a Node Bthrough a call setup process.

In step 410, the UE calculates a wake-up timing using the receivedinformation. The wake-up timing can be calculated using previouslydescribed Equation (1).

In step 415, the connected mode UE switches to the sleep mode, and keepsthe sleep mode until the calculated wake-up timing. At the wake-uptiming, the UE receives a particular downlink control channel in step425, and then proceeds to step 430 where the UE determines whether anincoming data indication is received. The particular downlink controlchannel can be a grant channel. Alternatively, the incoming dataindication can be sent over a downlink transmission resource allocationmessage.

As described above, the transmission resource allocation messagecontains (i) an identifier of the UE that will be allocated transmissionresources, (ii) information on the transmission resources to beallocated, and (iii) the other information. The UE and the Node B canreserve one of the code points in the other information and use the onecode point to indicate the incoming data indication. Further, the Node Bincludes, in the transmission resource information corresponding to theincoming data indication, information on the channel over which the UEwill perform channel quality report.

Upon failure to receive the incoming data indication in step 430, the UEproceeds to step 435 where it switches to the sleep mode, and then keepsthe sleep mode until the next wake-up timing.

However, upon receipt of the incoming data indication in step 430, theconnected mode UE proceeds to step 440 where the UE starts a T1 timerand a T2 timer. The t1 and t2 signaled in the call setup process areinput to the T1 timer and the T2 timer, respectively.

If needed, the UE performs an uplink synchronization establishmentprocess according to a particular scheme in step 445. That is, the UEtransmits a preamble over a particular uplink shared channel, and theNode B transmits transmission timing adjustment information over aparticular downlink channel. Then the UE adjusts the transmission timingaccording to the transmission timing adjustment information.

In step 447, the UE enters the sleep mode and then keeps the sleep modeuntil the T2 timer expires after completing the above process. If the T2timer expires, the UE proceeds to step 450 where the UE reports ChannelQuality Indication (CQI) according to a particular scheme. The UE cantransmit the CQI using transmission resources corresponding to thetransmission resource information transmitted together with the incomingdata indication.

Thereafter, in step 455, the UE switches to the sleep mode and keeps thesleep mode until the T1 timer expires. If the T1 timer expires, the UEreceives, in step 460, allocated downlink transmission resources over agrant channel, and receives data over the allocated downlinktransmission resources.

The UE performs in step 465 the data reception until the UE receives asignal indicating an end of the data transmission from the Node B. Uponreceipt of the signal indicating the end of the data transmission fromthe Node B, the UE proceeds to step 470 where the UE switches to thesleep mode and then keeps the sleep mode until the next wake-up timing.

In the first example of the present invention, as shown in FIGS. 3 and4, the Node B should separately send the incoming data indication andthe downlink transmission resource allocation message to transmit datato the connected mode UE in the DRX mode.

A second example of the present invention is shown in FIGS. 5 and 6, andprovides a method for sending incoming data indication together withtransmission resource allocation information to be used for datatransmission/reception, thereby avoiding separately sending a downlinktransmission resource allocation message.

The second example of the present invention sends the incoming dataindication together with transmission resource allocation informationallocated after t3, so the UE can perform downlink data receptionwithout the need to receive separate transmission resource allocationinformation after establishing uplink synchronization. The secondexample of the present invention can be applied to the services that donot need to make a separate CQI report because the amount of generateddata is small.

FIG. 5 shows a DRX operation of a connected mode UE according to thesecond example of the present invention.

In FIG. 5, in a call setup process, a UE receives DRX-related parameterssignaled from a Node B. The UE calculates a wake-up timing using theDRX-related parameters. The DRX-related parameters can include thefollowing, for example, a DRX cycle length 510, first wake-up timingcalculation information, t3, etc.

The DRX cycle length 510 indicates a length of a period between wake-uptimings, and the Node B selects an appropriate value according to typesof services. The Node B uses a long DRX cycle length which is longerthan predetermined length for the services less susceptible to thedelay, and a short DRX cycle length which is shorter than predeterminedlength for the services highly susceptible to the delay.

First wake-up timing calculation information may include the firstwake-up timing that can be directly signaled to the UE, or the UE cancalculate the first wake-up timing by combining the identifier of theUE, the DRX cycle length, etc.

The t3 indicates information on the timing at which the transmissionresource information included in the incoming data indication isactually applied.

After the call setup is completed, the UE calculates the first wake-uptiming, and calculates the next wake-up timing by adding a length of theDRX cycle to the first wake-up timing.

The connected mode UE keeps the sleep mode until the wake-up timing, andmonitors a downlink control channel at a wake-up timing 515. If the UEfails to receive the incoming data indication over the downlink controlchannel for a particular period in step 530, the UE transitions back tothe sleep mode and keeps the sleep mode until the next wake-up timing520.

After transitioning to the sleep mode, the UE re-monitors the downlinkcontrol channel at the next wake-up timing 520. In this case, if theNode B recognizes that it has data stored in a buffer to transmit to theUE, the Node B sends an incoming data indication to the UE at thewake-up timing 520 in step 540). At this point, the Node B transmits tothe UE even the transmission resource allocation information to be usedafter t3.

Therefore, upon receipt of the incoming data indication, the UE that haswaken up at the wake-up timing 520, starts a timer to which the t3 isinput, and performs an uplink synchronization establishment operation instep 545. In this case, the UE can skip the uplink synchronizationestablishment process when the UE determines that the uplinksynchronization has already been established.

After completing the uplink synchronization establishment, the UEswitches back to the sleep mode and keeps the sleep mode until the t3expires. If the t3 expires in step 570, the UE receives the data overthe transmission resources allocated while receiving the incoming dataindication in step 560, and performs an HARQ process on the transmitteddata in step 565.

Thereafter, upon receiving from the Node B information (signal)indicating that there is no more transmission data, the UE switches tothe sleep mode and keeps the sleep mode until the next wake-up timing525.

FIG. 6 shows a DRX operation of a connected mode UE according to thesecond example of the present invention.

In step 605 of FIG. 6, a UE receives DRX cycle length, first wake-uptiming calculation information, and t3 signaled from a Node B through acall setup process.

In step 610, the UE calculates a wake-up timing using the receivedinformation. The wake-up timing can be calculated using the previouslydescribed Equation (1).

In step 615, the UE switches to the sleep mode, and keeps the sleep modeuntil the calculated wake-up timing. At a particular wake-up timing, theUE receives a particular downlink control channel in step 625, and thenproceeds to step 630 where the UE determines whether an incoming dataindication is received over the downlink control channel. The incomingdata indication can contain the downlink transmission resourceinformation that the UE can use after the time t3.

The incoming data indication can be sent over a downlink transmissionresource allocation message. The downlink transmission resourceinformation that the UE can use after the time t3, is contained in atransmission resource information field of the downlink transmissionresource allocation message.

Therefore, the downlink transmission resource allocation message thatthe UE has received at the particular wake-up timing is recognized notas the general downlink transmission resource allocation message, but asa transmission resource allocation message including incoming dataindication. Since the incoming data indication uses a code pointreserved in the other information of the downlink transmission resourceallocation message, the incoming data indication can be distinguishedfrom the general transmission resource allocation message.

Upon failure to receive the incoming data indication in step 630, the UEproceeds to step 635 where the UE switches back to the sleep mode andthen keeps the sleep mode until the next wake-up timing. However, uponreceipt of the incoming data indication in step 630, the UE proceeds tostep 640 where the UE starts a T3 timer. The t3 signaled in the callsetup process is input to the T3 timer.

If needed, the UE performs an uplink synchronization establishmentprocess according to a particular scheme in step 645, and then proceedsto step 655 where the UE switches to the sleep mode and keeps the sleepmode until the T3 timer expires.

After the T3 timer expires, the UE receives in step 660 the data overthe downlink transmission resources allocated in the incoming dataindication. In step 665, the UE performs the data reception until asignal indicating an end of the data transmission is received from theNode B. Upon receipt of the signal indicating the end of the datatransmission from the Node B, the UE proceeds to step 670 where itswitches back to the sleep mode and keeps the sleep mode until the nextwake-up timing.

A third example of the present invention is shown in FIGS. 8 and 9 thatprovides a process in which upon receipt of an incoming data indication,a connected mode UE establishes uplink synchronization with a Node B.

However, in a conventional mobile communication system, the actualuplink synchronization establishment process is defined for an idle modeUE. Therefore, to establish uplink synchronization according to theconventional uplink synchronization establishment rule in a mobilecommunication system is very inefficient for a connected mode UE.

Therefore, the third example of the present invention provides a schemein which upon receipt of an incoming data indication, the connected modeUE establishes uplink synchronization with the Node B. Before adescription of the third example of the present invention is given, abrief description of a conventional uplink synchronization establishmentprocess of the idle mode UE will be made with reference to FIG. 7.

Referring to FIG. 7, upon detecting the need to establish uplinksynchronization, an arbitrary UE 705 randomly selects one arbitrarysignature from a set of known signatures. The signatures are codes whichare orthogonal with each other, and serve for temporarily identifyingUEs in the uplink synchronization establishment process in step 715.

Upon detecting an uplink signal coded with an arbitrary signature, aNode B 710 recognizes that an arbitrary UE has started an uplinksynchronization establishment process, and communicates with the UE overthe signature until the Node B 710 checks a real identifier of the UE.

That is, the UE codes a preamble using the randomly selected signature,and then transmits the randomly selected signature to the Node B at aparticular timing in step 720, and upon detecting the preamble codedwith the signature, the Node B determines a transmission timingadjustment value (timing adjustment). Further, the Node B allocates aCell Radio Network Temporary Identity (C-RNTI), or an identifier thatthe UE will use in the connected mode in step 725, determines uplinktransmission resources that the UE will use for sending of an uplinkcontrol message, and then sends a control message containing thedetermined uplink transmission resource information to the UE in step730. The control message is sent over the general data channel in step730.

When transmitting the data over the data channel of step 730, the Node Bfirst allocates transmission resources to the UE over a downlink controlchannel, referred to herein as an L1/L2 control channel, and transmitsthe data over the allocated transmission resources. A C-RNTI of the UEis contained in the L1/L2 control channel to specify the UE to whichtransmission resources are allocated, or the C-RNTI is implicitlysignaled through Cyclic Redundancy Check (CRC) of the L1/L2 controlchannel.

However, because the Node B cannot have information on the C-RNTI of theUE now operating in the uplink synchronization establishment process,the Node B contains in the control message the information serving as anidentifier of the UE, and signals over the L1/L2 control channel acommon identifier indicating that the UE to which transmission resourcesare allocated is the UE that is performing the uplink synchronizationestablishment process in step 725.

The UE sends an uplink control message using the transmission resourcesallocated in step 730, and the uplink control message contains anidentifier, referred to herein as a fixed identifier, that can firmlyidentify the UE in step 735. For example, the fixed identifier can beeither an identifier unique all over the world like the InternationalMobile Subscribe Identity (IMSI), or an identifier unique all over arelatively broader area like the Temporary Mobile Subscribe Identity(TMSI).

If multiple UEs transmit preambles using the same signature in step 720,the given information is information unique to only one UE among themultiple UEs, and the other UEs should re-perform the uplinksynchronization establishment process.

To simultaneously transmit preambles using the same signature by themultiple UEs in this way is expressed that a collision has occurred.There is a need for a procedure for detecting that no collision hasoccurred. To detect that no collision has occurred, the Node B transmitsthe fixed identifier of the UE over the downlink in step 740, and the UEends the uplink synchronization process after the fixed identifier ofthe UE is transmitted over the downlink.

As described above, the conventional uplink synchronizationestablishment process of the idle mode UE is unsuitable for the UE thatperforms the uplink synchronization establishment process, because theUE already has the C-RNTI and the UE having no control message to sendover the uplink receives an incoming data indication from the Node Bwhile performing the DRX operation in, for example, the connected mode.

That is, the third example of the present invention uses an uplinksynchronization establishment process distinguishable from thesynchronization establishment process of FIG. 7, after receiving theincoming data indication.

FIG. 8 shows a DRX operation of a connected mode UE according to thethird example of the present invention. In particular, the uplinksynchronization establishment process of FIG. 8 performs temporarymapping between dedicated signature and C-RNTI.

Referring to FIG. 8, if a Node B 810 has data to transmit to a connectedmode UE 805 now in a DRX operation, it sends an incoming data indicationto the UE at a particular timing in step 815. The incoming dataindication contains the dedicated signature information that the UE willuse in the uplink synchronization establishment process.

The present invention will now be described based on the assumption thatone cell uses 64 signatures. Therefore, the information indicating thededicated signature can be expressed with 6 bits. In addition, thededicated signature should not be used by another UE for the time whenthe connected mode UE 805 performs the uplink synchronizationestablishment process. Accordingly, the dedicated signature should notbe included in the shared signature set.

Upon receipt of the incoming data indication in step 815, the UE 805transmits a preamble coded with the dedicated signature at the slotlocated closest to the timing, among the slots defined for transmittingpreambles in step 820.

The Node B 810 has already recognized which timing and signature the UE805 will use in transmitting the preamble. Therefore, upon detecting thepreamble coded with the dedicated signature, the Node B 810, determiningthat the UE 805 is performing the uplink synchronization establishmentprocess, contains in an L1/L2 control channel a C-RNTI of the UE 805 orimplicitly signals the C-RNTI of the UE 805 through CRC of the L1/L2control channel in step 825, thereby notifying that the data transmittedin step 830 is data transmitted to the UE 805.

Because the C-RNTI of the UE is used herein for the L1/L2 controlchannel, other UEs performing the uplink synchronization establishmentprocess do not receive the data transmitted in step 830, therebypreventing the collision. The control message transmitted in step 830,i.e. the control message transmitted in response to the preamble codedwith the dedicated signature, contains a transmission timing adjustmentvalue and information on a CQI channel that the UE will use in thefuture.

The UE 805 adjusts a transmission timing according to the transmissiontiming adjustment value in step 835, and performs CQI transmissionaccording to the CQI channel information in step 840.

If it is determined that the uplink synchronization establishmentprocess is completed, the Node B 810 transmits downlink data to the UE805 in step 845.

FIG. 9 shows an operation of a UE according to the third example of thepresent invention.

In step 905 of FIG. 9, the UE receives an incoming data indication and adedicated signature at a particular timing.

In step 910, the UE transmits a preamble coded with the dedicatedsignature at the slot located closest to the timing, among the slotsdefined for transmitting preambles, and then proceeds to step 915 wherethe UE monitors whether L1/L2 control information matched to its ownC-RNTI is received.

For this, upon receipt of the preamble coded with the dedicatedsignature, a Node B decides to configure a CQI channel allocated to theUE, determines transmission timing adjustment information to be appliedto the UE, and configures a control message containing the information.Further, the Node B sends the control message to the UE with a schemecorresponding to the general data transmission process. That is, in step915, the Node B signals, over the L1/L2 control channel, transmissionresources over which the C-RNTI of the UE and the control message willbe transmitted, and sends the control message over the transmissionresources.

Therefore, the UE, while monitoring the L1/L2 control channeltransmitted from the Node B, receives the control message in step 920,and establishes uplink synchronization depending on transmission timingadjustment information contained in the control message in step 925.

The UE sends CQI information at a particular timing according to thesignaled CQI channel configuration information in step 930, and monitorsthe L1/L2 control channel to receive the data transmitted by the Node Bin step 935. Further, the UE, while receiving the data transmitted bythe Node B, resumes the DRX operation according to a particularprocedure. That is, if the data reception is done, the UE transitions tothe sleep mode in step 940.

FIG. 10 shows a reception apparatus 1000 of a UE according t the presentinvention.

The reception apparatus 1000 of FIG. 10 includes a demultiplexer (DEMUX)1005, an HARQ processor 1015, a receiver 1040, an uplink synchronizationcontroller 1025, a control channel processor 1020, a channel qualityreporter 1030, and a DRX controller 1035.

The receiver 1040 is turned ON/OFF under the control of the DRXcontroller 1035. The DRX controller 1035 calculates wake-up timingsusing DRX-related parameters, and then turns ON the receiver 1040 at thewake-up timing. If the valid period expires, the DRX controller 1035turns OFF the receiver 1040 until the next wake-up timing.

The HARQ processor 1015 processes an HARQ packet that the receiver 1040receives through a particular HARQ operation, and forwards theerror-free HARQ packet to the demultiplexer 1005. The demultiplexer 1005demultiplexes the received HARQ packet to an appropriate upper layer.

Upon receipt of an incoming data indication over a received controlchannel, the control channel processor 1020 reports this to the uplinksynchronization controller 1025 and the channel quality reporter 1030.

Upon receipt of the incoming data indication, the uplink synchronizationcontroller 1025 determines whether there is a need for uplinksynchronization reestablishment, and if there is a need to reestablishthe uplink synchronization, the uplink synchronization controller 1025reestablishes uplink synchronization through a particular procedure.

Therefore, according to the first example of the present invention, thechannel quality reporter 1030 reports a channel quality over aparticular channel after a lapse of T2 from the timing when the incomingdata indication was received. In addition, after a lapse of T1 from thetiming when the incoming data indication was received, the DRXcontroller 1035 turns ON the receiver 1040 to receive a transmissionresource allocation message, and receives the downlink data over theallocated transmission resources.

According to the second example of the present invention, after lapse ofT3 from the timing when the incoming data indication was received, theDRX controller 1035 turns ON the receiver 1040 to receive the data.

According to the third example of the present invention, the DRXcontroller 1035 turns ON the receiver 1040 to receive the data dependingon the transmission timing adjustment information included in L1/L2control information matched to the C-RNTI allocated thereto. Upondetecting an end of the data reception for the time designated in thetransmission timing adjustment information, the DRX controller 1035turns OFF the receiver 1040.

According to the present invention, to support a next generation mobilecommunication system, the connected mode UE, when the UE operates in theDRX mode, reports the channel quality of the UE after determiningwhether there is transmission of actual data. Therefore, the presentinvention prevents the connected mode UE from unnecessarily periodicallyreporting the channel quality. In addition, the present invention usesthe wireless resources wasted for the periodic channel quality report,for transmission of other information, or uses the saved wirelessresources for other services, thereby increasing an efficiency of thelimited wireless resources.

In addition, the present invention increases an efficiency of the DRXmode of the connected mode UE, thereby minimizing power consumption ofthe UE. The minimization of the power consumption maximizes the latencytime of the UE, contributing to an increase in the possible servicetime.

Further, the present invention prevents a collision by other UEs,occurring as the connected mode UE establishes uplink synchronizationupon receiving a dedicated signature expressed with a particular bit.

While the invention has been shown and described with reference tocertain preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

What is claimed is:
 1. A method for establishing Time Alignment by aUser Equipment (UE) in a wireless communication system, the methodcomprising: receiving, from a base station, information for identifyinga dedicated preamble on a downlink control channel; transmitting, to thebase station, the dedicated preamble based on the information;receiving, from the base station, a response message to the transmitteddedicated preamble on a downlink shared channel, wherein the responsemessage includes a timing adjustment information and information for aChannel Quality Indicator (CQI) report; establishing Time Alignmentbased on the timing adjustment information included in the responsemessage; and transmitting, to the base station, the CQI report based onthe information for CQI report.
 2. The method of claim 1, wherein theinformation for CQI report comprises information on resource assignmentfor the CQI report.
 3. The method of claim 1, further comprising:receiving, from the base station, downlink data after establishing TimeAlignment.
 4. The method of claim 1, wherein the response messagefurther comprises an uplink grant.
 5. A User Equipment (UE) forestablishing Time Alignment in a wireless communication system, the UEcomprising: a transceiver for receiving, from a base station,information for identifying a dedicated preamble on a downlink controlchannel, transmitting the dedicated preamble based on the information tothe base station, receiving from the base station a response messagecorresponding to the transmitted dedicated preamble on a downlink sharedchannel and transmitting a Channel Quality Indicator (CQI) report to thebase station, wherein the response message includes a timing adjustmentinformation and information for the CQI report; and a controlleroperable to establish Time Alignment based on the timing adjustmentinformation included in the response message and to transmit, to thebase station, the CQI report based on the information for the CQIreport.
 6. The UE of claim 5, wherein the information for the CQI reportcomprises information on resource assignment for the CQI report.
 7. TheUE of claim 5, wherein the transceiver receives downlink data from thebase station after establishing Time Alignment.
 8. The UE of claim 5,wherein the response message further comprises an uplink grant.
 9. Amethod for establishing Time Alignment by a base station in a wirelesscommunication system, the method comprising: transmitting, to a UserEquipment (UE), information for identifying a dedicated preamble on adownlink control channel; receiving, from the UE, the dedicated preamblebased on the information; transmitting, to the UE, a response messagecorresponding to the transmitted dedicated preamble on a downlink sharedchannel, wherein the response message includes timing adjustmentinformation for establishing Time Alignment and information for aChannel Quality Indicator (CQI) report; and receiving, from the UE, theCQI report based on the information for CQI report.
 10. The method ofclaim 9, wherein the information for CQI report comprises information onresource assignment for the CQI report.
 11. The method of claim 9,further comprising: transmitting downlink data to the UE afterestablishing Time Alignment.
 12. The method of claim 9, wherein theresponse message further comprises an uplink grant.
 13. A base stationfor establishing Time Alignment in a wireless communication system, thebase station comprising: a transceiver for transmitting, to a UserEquipment (UE), information for identifying a dedicated preamble on adownlink control channel, receiving, from the UE, the dedicated preamblebased on the information, transmitting, to the UE, a response messagecorresponding to the transmitted dedicated preamble on a downlink sharedchannel, and receiving, from the UE, a Channel Quality Indicator (CQI)report, and a controller operable to generate the response messageincluding timing adjustment information for establishing Time Alignmentand information for the CQI report, and to receive, from the UE, the CQIreport based on the information for the CQI report.
 14. The base stationof claim 13, wherein the information for the CQI report comprisesinformation on resource assignment for the CQI report.
 15. The basestation of claim 13, wherein the transceiver transmits downlink data tothe UE after establishing Time Alignment.
 16. The base station of claim13, wherein the response message further comprises an uplink grant.